Biomedical subjects

Haitham A Hussain

Publications and source records attributed to Haitham A Hussain.

3 recordsLinked to original sources

PubMed2007

Genetic variation in comC, the gene encoding competence-stimulating peptide (CSP) in Streptococcus mutans.

The genetic variability in comC, the gene encoding the quorum-sensing molecule, competence-stimulating peptide (CSP) in Streptococcus mutans is reported. Seven comC alleles encoding three distinct mature CSPs were identified among 36 geographically diverse strains, although, compared with Streptococcus pneumoniae, the amount of predicted amino acid sequence variation is low. In agreement with other studies, significant variation was found in the natural competence for DNA uptake in these strains. However, there was no correlation between the CSP genotype and the ability to transform these strains. Representative strains encoding each of the CSP variants became competent in response to synthetic CSPs of each type. Therefore, in contrast to S. pneumoniae, comC alleles in S. mutans are functionally equivalent and there is no evidence of pherotype specificity.

Alleles↗

PubMed2005

Generation of an erythromycin-sensitive derivative of Clostridium difficile strain 630 (630Deltaerm) and demonstration that the conjugative transposon Tn916DeltaE enters the genome of this strain at multiple sites.

Erythromycin resistance in Clostridium difficile strain 630 is conferred by a genetic element termed Tn5398 which contains two erm(B) genes: erm1(B) and erm2(B). An erythromycin-sensitive derivative of strain 630 (designated 630Deltaerm) was generated by spontaneous mutation after continuous subculture for 30 days. This strain had lost the erm2(B) gene from within Tn5398 but retained erm1(B). However, the strain could revert to erythromycin resistance at a frequency of 2.79 x 10(-8), although it still contained the deletion of erm2(B). The availability of C. difficile 630Deltaerm allowed the behaviour of Tn916DeltaE to be investigated in this strain. This element entered the genome at multiple sites indicating that it could be useful as an insertional mutagen.

Blotting, Southern↗

PubMed2003

Enhanced heterologous expression of two Streptomyces griseolus cytochrome P450s and Streptomyces coelicolor ferredoxin reductase as potentially efficient hydroxylation catalysts.

The herbicide-inducible, soluble cytochrome P450s CYP105A1 and CYP105B1 and their adjacent ferredoxins, Fd1 and Fd2, of Streptomyces griseolus were expressed in Escherichia coli to high levels. Conditions for high-level expression of active enzyme able to catalyze hydroxylation have been developed. Analysis of the expression levels of the P450 proteins in several different E. coli expression hosts identified E. coli BL21 Star(DE3)pLysS as the optimal host cell to express CYP105B1 as judged by CO difference spectra. Examination of the codons used in the CYP1051A1 sequence indicated that it contains a number of codons corresponding to rare E. coli tRNA species. The level of its expression was improved in the modified forms of E. coli BL21(DE3), which contain extra copies of rare codon E. coli tRNA genes. The activity of correctly folded cytochrome P450s was further enhanced by cloning a ferredoxin reductase from Streptomyces coelicolor downstream of CYP105A1 and CYP105B1 and their adjacent ferredoxins. Expression of CYP105A1 and CYP105B1 was also achieved in Streptomyces lividans 1326 by cloning the P450 genes and their ferredoxins into the expression vector pBW160. S. lividans 1326 cells containing CYP105A1 or CYP105B1 were able efficiently to dealkylate 7-ethoxycoumarin.

Bacterial Proteins↗